Fusion Science and Technology / Volume 51 / Number 4 / May 2007 / Pages 530-538
In ablator shell fabrication, trace elements and impurities are introduced in the deposition and the pyrolysis process, which must be controlled below a critical level. However, it is the opacity, not the individual elements, which matters in an Inertial Confinement Fusion (ICF) implosion. Radiography measures the opacity, allowing the accurate determination of the total impurity effect in a lump sum. Furthermore, by using the sputter target trace element information, we can determine the radial profile of oxygen to ±0.4 at. %. Oxygen is very difficult to measure by any other method, but is critically important for beryllium process development such as mandrel removal. To ensure measurement accuracy, we use a local standard to remove fluctuation in film developing and a step wedge to calibrate the film model.